A need exists in industry for non-destructive inspection of composite structures assembled with adhesive bonds. Among other techniques, laser bond inspection (LBI) has proven useful. Normally, LBI involves deposition of laser energy onto the front surface of a first plate in a bonded article, generating compression waves that reflect off of the back surface of the bonded article as tensile waves, the tensile waves predominantly providing the stresses that interrogate the bond. The compression waves are generally longitudinal, having been driven normal to the plane of the first plate.
In a number of tasks, the use of longitudinal stress waves as generated in conventional LBI is impractical. For example, in circumstances where the first plate has a materially different acoustic impedance than the plate(s) or structure to which the first plate is bonded, the results (i.e., bond breaking and detection of bond breaking) can be inconsistent. Another exemplary circumstance may be where the bond to be tested is a face-sheet-to-core bond, wherein no back free surface is accessible to generate a tensile wave.